Selective Catalysis with Macrocyclic Nitrogen Ligands

With the support of the Chemical Catalysis Program in the Division of Chemistry, Professor Steven T. Diver of the University at Buffalo is studying the synthesis and use of special macrocyclic ligands to enable metal-based catalysts to perform selective chemical reactions. The combinations of metals and such relatively unexplored macrocyclic ligands will be investigated with the aim of achieving selectivity based upon molecular size. This selectivity principle is a common facet of Nature's catalysts (enzymes), but it represents a challenging frontier for artificial small-molecule catalysts. Success in the endeavors being pursued, which involve earth abundant and low cost metals, will allow for the manufacture of important commodities, such as fine chemicals, pharmaceutical agents, agrochemicals, and other advanced materials of value to the US economy, to be conducted in a more efficient and sustainable manner. The broader impacts of the funded project will extend to the development of a certification program aimed at improving the training of graduate students who are headed towards careers in teaching. In such endeavors, the PI has an excellent record of successfully mentoring a diverse group of mentees. A workshop focused on fostering more effective faculty mentorship is also planned with the expectation of enhancing the performance of teaching and research activities at SUNY Buffalo. The funded project focuses on further development of the concept of size-selective catalysis using complexes of Fe, Co, or Ni, and specially designed macrocyclic ligand families for various cross coupling and hydrofunctionalization reactions. The work builds on previous studies by the Diver research group in which macrocyclic N-heterocyclic carbene ligands were demonstrated for size-selective Ru-catalyzed alkene metathesis. The ability of a catalyst to distinguish between two of the same functional groups within a molecule will allow organic synthesis to be planned and carried out in new ways, potentially obviating (or at least minimizing) the need for extraneous operations involving protecting group and other wasteful synthetic manipulations. The research program is divided across several synergistic aims; in each case, the size selectivity principles previously established will be extended and adapted for catalysts based on earth abundant metals by using new macrocyclic systems that feature bidentate or tridentate nitrogen-containing ligands. For example, macrocyclic and bimacrocyclic phenanthroline ligands will be synthesized and used in Ni- and Co-catalyzed cross coupling and in the Fe-catalyzed hydrosilylation of alkenes. In other work, macrocycles will be utilized for size-selective oxidation to differentiate secondary alcohols within polyol substrates. The transformations being studied are industrially relevant and the findings of this research are expected to highlight efficient and economical alternatives to noble metals for chemical manufacturing. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.